A pulsed EPR study of clustering of Yb 3+ ions incorporated in GeO 2 glass

Abstract

The structural aspects of clustering of Yb 3+ ions and the paramagnetic behavior of these clusters have been investigated in GeO 2 glasses doped with 140–1100 ppm by weight of Yb 2O 3 using time-domain electron paramagnetic resonance (EPR) spectroscopic techniques. The echo-detected EPR (EDEPR) spectra of Yb 3+ ions and their unusual dependencies on microwave power and magnetic field have been found to be indicative of the formation of clusters of these rare earth ions in GeO 2 glass that behave as non-Kramers type spin systems. The magnetic field and concentration dependence of phase relaxation rates of Yb 3+ in these glasses further substantiate such a scenario and indicate the formation of clusters of Yb 3+ ions. A comparison of the EDEPR spectra with calculated cw-EPR line shapes yields a semi-quantitative measure of the typical cluster size of ⩾3 Yb atoms and intra-cluster Yb–Yb distances of 3.5–4.0 Å in these glasses at doping levels of ⩾350 ppm of Yb 2O 3.